Alternator voltage regulator keeps going bad

EvaNeedsHelpNow · Sep 26, 2020

Hello ,
Please help ! Have a 2010 Jeep Liberty Sport . Recently the battery light came on and when I went to leave my driveway one day all my lights came on the dash and it died . Had another battery already so put it on and took it to get my battery and alternator tested showed battery was fine both of them but my voltage regulator was bad I am now on alternator number 4 and still having same issue can drive for a short distance the battery light comes on and it will eventually die on me .The things we have tried besides the alternator (epic fail) is the ground wires well to be exact have replaced the entire battery wire harness and connectors and cleaned all the connections to the jeep itself as far as the ground wires where concerned .The fusible link was blown as well as some bad wires along the pathway of the grounds all new now but once started it up the battery light came on quicker than before are currently replacing alternator number 5 now hoping that since we replaced the wires that it will be ok ??? Fingers and toes crossed ! Have done a reset of the tipm and the pcm so not sure what else to do oh yeah checked fuses only a fuse to cig lighter was bad all relays where ok too so any other things that need to be tested and how to do so would be greatly appreciated .While running the battery will show the voltage dropping not running holds at 12.56 most of the time just don't crank it up cause it will keep going down add lights or anything extra and it really goes down that is using a multimeter to test while running . Please Help cause I'm to the point of thinking my step to do for it is to buy some matches and a can of gas and be done with the stress but I need my vehicle too much for that but then again it isn't doing me any good just sitting in my driveway looking pretty ?? HELP PLEASE???

tommudd · Sep 26, 2020

Are you sure the PCM is good ?

Billwill · Sep 27, 2020

Not good that the Fuse-able Link blew....this is the wire that charges the battery and any short to engine/chassis stops the charging. You need to make sure that there is no way that this Link can touch ground.
Also fitting this Link onto the positive battery post or onto the alternator without first disconnecting the battery can blow the link.

Make sure you have the correct color link instaled...I am not familiar with the 2010 KK but historically the links have different colors for various models and have a different fuse rating.

At the end of the KJ run there were lots of changes made to the way the batteries were charged. At first the Alternators had an exciter coil that was controlled by the PCM/ECM with a saw-tooth wave to increase/decrease the charging voltage.

Then some models had the voltage control built into the Alternator.
In some cases the alternator was turned off while the engine turned over so as to lessen drag on the engine and would then start charging after a few seconds....the PCM would send a "wake up call" to the alternator.

The very early KJs had a Battery Temperature Sensor under the battery that adjusted the charge silghtly...this was dropped as it caused a lot of problems...doubt that it has returned.

If someone can give me a link to the 2010 KK Wiring Diagrams I can look into it.

In the meantime:

Make sure you definitely have the correct Alternator for your vehicle.

Make sure the Fusable Link has not blown.

Make sure the engine and body are correctly grounded to the negative battery lead...add extra thick wires if needed.

Check the leads coming from the Alternator to the PCM are not touching onto engine/chassis.

Replace the PCM if needed.

Put your Voltmeter into the front Power Outlet so you can monitor the charging voltage while driving...if it is not at about 13.4 volts with engine running you may as well turn back home because the battery will rapidly go flat!

I have seen some posts on some Jeep sites where owners fitted an external regulator to charge the battery and made sure the Alternator only had the rectifier diodes installed.

Edit to add: I see that you say that the Voltage Regulator was bad....is this Regulator inside the Alternator? The small plug on the Alternator..if it exists....how many leads does it have on it?

Those leads need to be traced to the PCM and checked for good connections and no rubbing of insulation through to engine/chassis.!

If you are on Alternator #4 now I think it is time to take the Jeep to another shop or Heaven Forbid to a Dealer!

Or have the PCM tested or replaced.

Billwill · Sep 28, 2020

Anybody have Wiring Diagrams for this 2010 KK for me so I can help out here?

lfhoward · Sep 28, 2020

Billwill said:
Anybody have Wiring Diagrams for this 2010 KK for me so I can help out here?

https://www.jeepkj.com/threads/factory-service-manual-links-kk.74533/

Billwill · Sep 28, 2020

EvaNeedsHelpNow said:
Hello ,
Please help ! Have a 2010 Jeep Liberty Sport . Recently the battery light came on and when I went to leave my driveway one day all my lights came on the dash and it died . Had another battery already so put it on and took it to get my battery and alternator tested showed battery was fine both of them but my voltage regulator was bad I am now on alternator number 4 and still having same issue can drive for a short distance the battery light comes on and it will eventually die on me .The things we have tried besides the alternator (epic fail) is the ground wires well to be exact have replaced the entire battery wire harness and connectors and cleaned all the connections to the jeep itself as far as the ground wires where concerned .The fusible link was blown as well as some bad wires along the pathway of the grounds all new now but once started it up the battery light came on quicker than before are currently replacing alternator number 5 now hoping that since we replaced the wires that it will be ok ??? Fingers and toes crossed ! Have done a reset of the tipm and the pcm so not sure what else to do oh yeah checked fuses only a fuse to cig lighter was bad all relays where ok too so any other things that need to be tested and how to do so would be greatly appreciated .While running the battery will show the voltage dropping not running holds at 12.56 most of the time just don't crank it up cause it will keep going down add lights or anything extra and it really goes down that is using a multimeter to test while running . Please Help cause I'm to the point of thinking my step to do for it is to buy some matches and a can of gas and be done with the stress but I need my vehicle too much for that but then again it isn't doing me any good just sitting in my driveway looking pretty ?? HELP PLEASE???

OK I have found some Manuals for these KKs thanks to ifhoward and will go through them. You mention a PCM which is for the 3.7 gasser....can you please confirm that this is a gasser and not a 2.8L Diesel!

Billwill · Sep 29, 2020

OK the 2008 KK manuals that I downloaded do not show a lot as regards the charging....the two wires in the small plug on the Alternator go into the PCM which controls the charging.

All I can suggest is:

Disconnect the battery.

Disconnect the small plug on the alternator.

Disconnect plugs C1 and C2 on the PCM....if you are not sure which are the C1 and C2 connectors then disconnect all connectors on the PCM

Take a Digital multi meter and put it on the Ohms setting.

Make sure you do not touch the meter leads with your bare hands as it affects the readings.

Measure each of the two wires from the alternator plug in turn for any continuity to engine/chassis...these wires are hanging in thin air and should not show any reading to ground unless there is a short.

The 2008 KK manual that I managed to down load shows the one wire to be Gray with a Red stripe and the other to be Brown with a Dark Green stripe but your 2012 KK may have different colors but that makes no difference.

If you get any reading to ground then physically trace the wires from end to end to look for scraping of the wires to metal.

The next step is to electrically measure each wire from end-to-end to see that they have no breaks. This is difficult to do as you cannot put your meter lead into the C1/C2 connector female pins as they are very small and you will damage them. The Dealers have a tool that plugs into the female sockets and expands to a larger plug that can be probed. If you can physically trace these wires from end to end you can tape a small pin or needle to one meter lead and carefully piece the insulation of the wire just before the C1 C2 plugs to check for continuity. You can cover up the holes made with some glue later....I have done this plenty times!

So the above steps check that there is no solid short to ground and no solid break but things may change when the engine is flexing while being driven!

If the above checks do not solve the problem I think you are going to have to take the Jeep to a Jeep Dealer as they have all the tools that are needed.

May end up that the Dealers end up fitting and programming a new PCM but you cannot keep on replacing Alternators!

BigJohn826 · Feb 19, 2022

Sounds very similar to what is happening to my KK right now. Did you ever figure it out?

Cuddlebugg · Aug 29, 2023

EvaNeedsHelpNow said:
Hello ,
Please help ! Have a 2010 Jeep Liberty Sport . Recently the battery light came on and when I went to leave my driveway one day all my lights came on the dash and it died . Had another battery already so put it on and took it to get my battery and alternator tested showed battery was fine both of them but my voltage regulator was bad I am now on alternator number 4 and still having same issue can drive for a short distance the battery light comes on and it will eventually die on me .The things we have tried besides the alternator (epic fail) is the ground wires well to be exact have replaced the entire battery wire harness and connectors and cleaned all the connections to the jeep itself as far as the ground wires where concerned .The fusible link was blown as well as some bad wires along the pathway of the grounds all new now but once started it up the battery light came on quicker than before are currently replacing alternator number 5 now hoping that since we replaced the wires that it will be ok ??? Fingers and toes crossed ! Have done a reset of the tipm and the pcm so not sure what else to do oh yeah checked fuses only a fuse to cig lighter was bad all relays where ok too so any other things that need to be tested and how to do so would be greatly appreciated .While running the battery will show the voltage dropping not running holds at 12.56 most of the time just don't crank it up cause it will keep going down add lights or anything extra and it really goes down that is using a multimeter to test while running . Please Help cause I'm to the point of thinking my step to do for it is to buy some matches and a can of gas and be done with the stress but I need my vehicle too much for that but then again it isn't doing me any good just sitting in my driveway looking pretty ?? HELP PLEASE???

My 2011 Jeep Liberty Limited is doing the same. I have spent close to $3500 trying to keep it running. Each time the Jeep dies on me the dealership says "oh, bring it back and we can take a look at it". I have taken it to them 3 times and each time I'm told everything is good except the alternator is going bad. I to am on my 4th alternator. Each time I take it back to the dealership, it is another 129.95 I have to give out. I am 60 years old, on disability and work a part time job driving a school bus. I have made SO many phone calls to different businesses trying to get answers, but no luck. Somebody please help us get this issue resolved.

Alternator voltage regulator keeps going bad

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